This project is a study of the molecular bases of the active transport of Na+ and K+. The mechanism of the Na, K-ATPase has been investigated using a rapid mixing technique for measuring the transient kinetics of its phosphorylation by ATP and subsequent dephosphorylation. We have shown that the manner in which oligomycin interacts with the enzyme provides evidence that the sodium pump functions as a dimer: under certain conditions only half of the subunits bind oligomycin. Regulation of sodium pump activity in brain is currently under study. We have developed rapid methods for measuring and analysing the kinetics of ouabain inhibition of the Na, K-ATPase. This method has allowed us to detect multiple forms of the sodium pump in brain membranes. A method for quantitatively extracting the Na, K-atPase from brain in soluble form has been developed. Molecular sieving studies indicate that this soluble form is a monodisperse component with an apparent molecular weight of about 1000 KDa. Current and future studies are directed at attempting to obtain a physical separation of the two major forms of Na, K-ATPase in brain and in further exploration of possible mechanisms which may regulate their levels of activity.